JP2021012983A - Wiring circuit board and manufacturing method of wiring circuit board - Google Patents

Abstract

To provide a wiring circuit board in which degradation in adhesibility of a second insulating layer to a first insulating layer under a moist heat condition can be suppressed, and furthermore reworkability of an electronic component can be ensured, and a manufacturing method of a wiring circuit board with high manufacturing efficiency.SOLUTION: A mounting board 1 comprises in a mounting substrate: a base insulating layer 4 containing polyimide, a development accelerator, and a photosensitizing agent; and a first terminal 10 arranged on one surface 4A of the base insulating layer 4, the sum of the content ratio of the development accelerator and the content ratio of the photosensitizing agent in the base insulating layer 4 is adjusted to 5 ppm or more and 50 ppm or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wiring circuit board and a method for manufacturing a wiring circuit board.

Conventionally, a wiring circuit board on which electronic components such as an image sensor are mounted is known.

For example, a base insulating layer having an image sensor opening, a conductor pattern having an image sensor connecting terminal, and a cover insulating layer are provided in this order, and the image sensor connecting terminal is exposed from the image sensor opening to cover the base insulating layer. An image sensor mounting substrate that is arranged so as to be flush with the surface opposite to the insulating layer has been proposed (see, for example, Patent Document 1).

On such an image sensor mounting substrate, the terminal of the image sensor and the image sensor connection terminal are connected by solder bumps on the surface of the base insulating layer opposite to the cover insulating layer, and the image sensor is mounted.

Further, in order to manufacture such an image sensor mounting substrate, first, a varnish of a photosensitive insulating material is applied onto a metal support and dried to form a base film, which is then exposed and developed into a predetermined pattern. , If necessary, heat-cured to form a base insulating layer.

As a material for such a base insulating layer, for example, a polyimide precursor composition containing a polyimide precursor, an imide acrylate compound as a development accelerator, and a pyridine-based photosensitive agent has been proposed (for example, Patent Documents). See 2.).

JP-A-2018-190787 Japanese Unexamined Patent Publication No. 2013-100441

However, in the image sensor mounting substrate as described in Patent Document 1, when an underfill layer is provided between the mounting surface and the image sensor from the viewpoint of improving the connection strength between the terminal of the image sensor and the image sensor connection terminal. There is.

However, when the base insulating layer is formed from the polyimide precursor composition described in Patent Document 2, the adhesion of the underfill layer to the base insulating layer is lowered under moist heat conditions, and the underfill layer is used for base insulation. May peel off from the layer.

Further, the image sensor mounted on the image sensor mounting substrate may be removed and reworked for replacement or reuse. In this case, it is desired to peel off the underfill layer from the base insulating layer. At this time, if the adhesion between the base insulating layer and the underfill layer is excessively high, it becomes difficult to peel off the underfill layer from the base insulating layer, and there is a problem that the reworkability of the image sensor cannot be ensured.

The present invention manufactures a wiring circuit board capable of ensuring reworkability of electronic components while suppressing a decrease in adhesion of the second insulating layer to the first insulating layer under moist heat conditions, and a wiring circuit board having high manufacturing efficiency. Provide a method.

The present invention [1] includes a first insulating layer containing a polyimide, a development accelerator, and a photosensitizer, and terminals arranged on one surface of the first insulating layer in the thickness direction. The total of the content ratio of the development accelerator and the content ratio of the photosensitizer in one insulating layer includes a wiring circuit board of 5 ppm or more and 50 ppm or less.

According to such a configuration, the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the first insulating layer is equal to or more than the above lower limit, so that the electronic component is placed on one surface in the thickness direction of the first insulating layer. Even if the wiring circuit board is placed under moist heat conditions with the second insulating layer provided between the first insulating layer and the electronic component after mounting, the adhesion of the second insulating layer to the first insulating layer is reduced. Can be suppressed.

Further, when the electronic component mounted on the wiring circuit board is removed from the wiring circuit board and reworked, the total of the content ratio of the development accelerator and the content ratio of the photosensitizer in the first insulating layer is not more than the above upper limit. The adhesion of the second insulating layer to the first insulating layer can be adjusted so that the second insulating layer can be peeled off from the first insulating layer, and the reworkability of the electronic component can be ensured.

The present invention [2] includes the wiring circuit board according to the above [1], wherein the development accelerator contains an imide acrylate compound and / or a polyethylene glycol compound.

According to such a configuration, since the development accelerator contains an imide acrylate compound and / or a polyethylene glycol compound, the total of the content ratio of the development accelerator and the content ratio of the photosensitizer in the first insulating layer is adjusted to the above range. While being possible, the photosensitivity of the varnish containing the polyimide precursor, the development accelerator, and the photosensitizer can be ensured.

The present invention [3] includes a step of preparing a metal support layer, a step of forming a first insulating layer containing a polyimide, a photosensitizer, and a development accelerator on the metal support layer, and the first step. The step of forming the first insulating layer includes a step of forming a terminal on one surface of the insulating layer in the thickness direction, and the step of forming the first insulating layer includes a polyimide precursor, a photosensitizer, and a development accelerator on the metal support layer. A wiring circuit board including a step of applying a varnish containing the above, a step of exposing and developing the varnish, and a step of heating the developed varnish to 300 ° C. or higher and 400 ° C. or lower for 100 minutes or longer. Including the manufacturing method of.

According to such a method, the developed varnish is heated to 300 ° C. or higher and 400 ° C. or lower for 100 minutes or longer. Therefore, the total of the content ratio of the photosensitizer and the content ratio of the development accelerator in the first insulating layer is 5 ppm. It can be adjusted to 50 ppm or less. As a result, the above-mentioned wiring circuit board can be efficiently manufactured even though it is a simple method.

According to the wiring circuit board of the present invention, it is possible to ensure reworkability of electronic components while suppressing a decrease in adhesion of the second insulating layer to the first insulating layer under moist heat conditions.

According to the method for manufacturing a wiring circuit board of the present invention, the above-mentioned wiring circuit board can be efficiently manufactured.

FIG. 1 shows a plan view of an image pickup device mounting board according to an embodiment of the wiring circuit board of the present invention. FIG. 2 shows a cross-sectional view taken along the line AA of the image sensor mounting substrate shown in FIG. 3A to 3D show a manufacturing process diagram of the image pickup device mounting substrate shown in FIG. 2, FIG. 3A is a metal support preparation step and a base insulating layer forming step, FIG. 3B is a conductor pattern forming step, and FIG. 3C is. , Cover insulating layer forming step, FIG. 3D shows a metal support removing step. 4E and 4F show a process diagram of mounting the image pickup device on the image pickup device mounting substrate following FIG. 3D, FIG. 4E shows the element connection step, and FIG. 4F shows the underfill forming step. FIG. 5 shows an image pickup apparatus including the image pickup device mounting substrate shown in FIG.

1. 1. Image sensor mounting board With reference to FIGS. 1 and 2, the image sensor mounting board 1 (hereinafter referred to as mounting board 1) as an embodiment of the wiring circuit board of the present invention will be described.

As shown in FIG. 1, the mounting board 1 is a flexible wiring circuit board (FPC) for mounting an image pickup device 21 (see FIG. 4F described later) as an example of an electronic component, and is still provided with the image pickup device 21. Not done. The mounting substrate 1 has a flat plate shape (sheet shape) that is substantially rectangular (rectangular) in a plan view.

The mounting board 1 includes a housing arrangement portion 2 and an external component connecting portion 3.

The housing arrangement portion 2 is a portion in which the housing 22 (described later, see FIG. 5) and the image sensor 21 are arranged. Specifically, the housing arrangement portion 2 is a portion that overlaps with the housing 22 when the housing 22 is arranged on the mounting substrate 1 and projected in the thickness direction of the mounting substrate 1. A plurality of first terminals 10 (described later) as an example of terminals are arranged substantially in the center of the housing arrangement portion 2.

The external component connecting portion 3 is an area other than the housing arranging portion 2 and is a portion for connecting to the external component. The external component connecting portion 3 is arranged continuously with the housing arranging portion 2 in the longitudinal direction of the mounting board 1. A plurality of second terminals 11 (described later) are arranged in the external component connecting portion 3.

As shown in FIG. 2, the mounting substrate 1 includes a base insulating layer 4 as an example of the first insulating layer, a conductor pattern 5, and a cover insulating layer 6 in order in the thickness direction of the base insulating layer 4. In the following, the thickness direction of the base insulating layer 4 is simply described as the thickness direction. In FIG. 2, the upper side of the paper surface is one side in the thickness direction of the base insulating layer 4, and the lower side of the paper surface is the other side in the thickness direction of the base insulating layer 4.

As shown in FIG. 1, the base insulating layer 4 has an outer shape of the mounting substrate 1 and has a substantially rectangular shape in a plan view. The base insulating layer 4 is not supported by the metal support 19 (see FIGS. 3A to 3C) described later, and the mounting substrate 1 does not include the metal support 19 (metal support layer).

The base insulating layer 4 includes a plurality of first openings 7 and a plurality of second openings 8.

The plurality of first openings 7 expose the first terminal 10 (described later) from one side in the thickness direction. The plurality of first openings 7 are arranged in a central portion of the housing arrangement portion 2 so as to form a rectangular frame at intervals of each other. The first opening 7 penetrates the base insulating layer 4 in the thickness direction and has a substantially circular shape in a plan view. The first opening 7 has a tapered shape in which the cross-sectional area of the opening decreases toward one side in the thickness direction (see FIG. 2).

The plurality of second openings 8 expose the second terminal 11 (described later) from one side in the thickness direction. The plurality of second openings 8 are arranged in the external component connecting portion 3 so as to be spaced apart from each other in the width direction of the mounting substrate 1. The second opening 8 penetrates the base insulating layer 4 in the thickness direction and has a substantially rectangular shape (rectangular shape) in a plan view.

Further, as shown in FIG. 2, the base insulating layer 4 includes one surface 4A and the other surface 4B in the thickness direction.

One surface 4A of the base insulating layer is located on one side in the thickness direction. One surface 4A of the base insulating layer has a flat (smooth) shape, and the entire surface thereof is exposed. The other surface 4B of the base insulating layer is located on the other side in the thickness direction and is located on the opposite side of the one surface 4A in the thickness direction. The other surface 4B of the base insulating layer is covered with the cover insulating layer 6.

Such a base insulating layer 4 contains a polyimide, a development accelerator, and a photosensitizer.

The polyimide is, for example, the polyimide described in JP-A-2018-190787, and contains a reaction product (cured product) of an acid dianhydride component and a diamine component. More specifically, polyimide is prepared by imidizing polyamic acid, which is a reaction product of an acid dianhydride component and a diamine component.

Examples of the acid dianhydride component include aromatic dianhydrides (eg, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA)) described in JP-A-2018-190787. (Biphenyltetracarboxylic dianhydride, etc.), and aliphatic acid dianhydride, etc. The acid dianhydride component can be used alone or in combination of two or more.

The acid dianhydride component preferably contains an aromatic acid dianhydride, and more preferably contains 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA). The acid dianhydride component is preferably composed of aromatic acid dianhydride (3,3', 4,4'-biphenyltetracarboxylic dianhydride).

Examples of the diamine component include aromatic diamines and aliphatic diamines described in JP-A-2018-190787. The acid dianhydride component can be used alone or in combination of two or more.

The diamine component preferably contains an aromatic diamine, and more preferably consists of an aromatic diamine.

Examples of the aromatic diamine include phenylenediamine such as p-phenylenediamine (PPD).

Further, two or more aromatic rings are bonded to the aromatic diamine by a single bond, and each of the two or more amino groups is bonded to a separate aromatic ring directly or as a part of a substituent. Aromatic diamine is also included. Such an aromatic diamine is represented by, for example, the following general formula (1).

(In the general formula (1), a is a natural number of 0 or 1 or more, R ¹ is a hydrogen atom or a substituent. The amino group is bonded to the meta position or the para position with respect to the bond between the benzene rings. .)
As substituents represented by R ¹ in the general formula (1), for example, an alkyl group having 3 or less carbon atoms such as a methyl group, for example, a trifluoromethyl group, perfluoroethyl group, carbon atoms, such as perfluoro propyl Examples thereof include a haloalkyl group of 3 or less (preferably a fluoroalkyl group), for example, a halogen atom such as chloro or fluoro.

In the above general formula (1), R ¹ preferably represents a substituent, more preferably a haloalkyl group, particularly preferably a fluoroalkyl group, and particularly preferably a trifluoromethyl group.

Specific examples of the aromatic diamine represented by the above general formula (1) include 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (also known as 2,2'-bis (trifluoromethyl)-. 4,4'-diaminobiphenyl, TFMB) and the like.

Such an aromatic diamine preferably contains a combination of phenylenediamine and the aromatic diamine represented by the general formula (1), and more preferably phenylenediamine and R ¹ in the general formula (1). Includes a combination with an aromatic diamine where is a fluoroalkyl group (trifluoromethyl group).

In such a diamine component, the content ratio of the aromatic diamine represented by the general formula (1) is, for example, 15 mol% or more, preferably 20 mol% or more, for example, 80 mol% or less, preferably 50 mol% or less. is there.

In addition, the acid dianhydride component contains 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the diamine component is phenylenediamine (PPD) and 2,2'-ditrifluoromethyl. When -4,4'-diaminobiphenyl (TFMB) is contained, the polyimide contains a structural unit A represented by the following general formula (2) and a structural unit B represented by the following general formula (3).

In such a polyimide, the mol ratio (structural unit A / structural unit B) of the structural unit A represented by the general formula (1) and the structural unit B represented by the general formula (2) is, for example, 15. / 85-80 / 20, preferably 20/80-50 / 50.

The development accelerator includes, for example, an imide acrylate compound and / or a polyethylene glycol compound.

The imide acrylate compound includes, for example, the imide acrylate compound described in JP2013-100441A.

Specifically, the imide acrylate compound is represented by the following general formula (4).

(In the general formula (4), R ² represents a hydrogen atom or a methyl group. R ³ represents a divalent hydrocarbon group having 2 or more carbon atoms.)
In the above general formula (4), R ² preferably represents a hydrogen atom.

In the above general formula (4), R ³ preferably represents an alkylene group having 2 or more carbon atoms, and more preferably an ethylene group.

Specific examples of the imide acrylate compound represented by the general formula (4) include n-acryloyloxyethyl hexahydrophthalimide and the like.

The polyethylene glycol compound includes, for example, the polyethylene glycol compound described in Japanese Patent Application Laid-Open No. 2013-100441.

Specifically, the polyethylene glycol compound is represented by the following general formula (5).

(In the general formula (5), R ⁴ represents a hydroxyl group or a methoxy group. R ⁵ represents a hydrogen atom or a methyl group. B represents a natural number of 4 to 23.)
In the above general formula (5), as a combination of R ⁴ and R ⁵ , a hydroxyl group (R ⁴ ) and a hydrogen atom (R ⁵ ), a hydroxyl group (R ⁴ ) and a methyl group (R ⁵ ), and a methoxy group (R) ⁴ ) and a methyl group (R ⁵ ), preferably a hydroxyl group (R ⁴ ) and a hydrogen atom (R ⁵ ).

The number average molecular weight (Mn) of the polyethylene glycol compound represented by the general formula (5) is, for example, 200 or more, for example, 1000 or less, preferably 400 or less. The number average molecular weight can be measured by gel permeation chromatography (GPC) method and can be calculated in terms of polyethylene oxide.

Such a development accelerator preferably comprises an imide acrylate compound represented by the above general formula (4).

The photosensitizer includes, for example, a pyridine-based photosensitizer described in Japanese Patent Application Laid-Open No. 2013-100441.

Specifically, the pyridine-based photosensitizer is represented by the following general formula (6).

(In the general formula (6), R ^{6 to} R ¹⁰ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ^{6 to} R ¹⁰ may be the same or different from each other.)
In the above general formula (6), each of R ⁶ and R ⁷ preferably represents a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

In the above general formula (6), R ⁸ preferably represents an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably an ethyl group.

In the above general formula (6), each of R ⁹ and R ¹⁰ preferably represents an alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. Shown.

Specific examples of the pyridine-based photosensitive agent represented by the general formula (6) include 1-ethyl-3,5-dimethoxycarbonyl-4- (2-nitrophenyl) -1,4-dihydropyridine. Can be mentioned.

The total (mass ratio) of the content ratio of the photosensitizer and the content ratio of the development accelerator in the base insulating layer 4 is 5 ppm or more and 50 ppm or less. The total of the content ratio of the photosensitizer and the content ratio of the development accelerator can be measured by TOF-SIMS (the same applies hereinafter).

When the sum of the content ratio of the photosensitizer and the content ratio of the development accelerator is equal to or higher than the above lower limit, the adhesion of the underfill layer 18 (described later) to the base insulating layer 4 is determined by the underfill layer 18 (described later). It can be adjusted so that it can be peeled off from the layer 4, and the reworkability of the image pickup device 21 can be ensured. Further, when the sum of the content ratio of the photosensitizer and the content ratio of the development accelerator is not more than the above upper limit, it is possible to suppress a decrease in the adhesion of the underfill layer 18 (described later) to the base insulating layer 4 under moist heat conditions.

In addition, the base insulating layer 4 can further contain a known additive. Known additives include, for example, sensitizers, polymerization inhibitors, chain transfer agents, leveling agents, plasticizers, surfactants, defoamers and the like. The content ratio of the known additive in the base insulating layer 4 is, for example, 15% by mass or less, preferably 10% by mass or less.

The thickness of the base insulating layer 4 is, for example, 1 μm or more, preferably 3 μm or more, for example, 30 μm or less, preferably 12 μm or less, and more preferably 8 μm or less.

The conductor pattern 5 includes a plurality of first terminals 10, a plurality of second terminals 11 (see FIG. 1), and a plurality of wirings 9.

The plurality of first terminals 10 are arranged and arranged at the center of the housing arrangement portion 2 so as to form a rectangular frame at intervals of each other (see FIG. 1). The plurality of first terminals 10 are provided so as to correspond to the plurality of terminals 25 (see FIG. 4E) of the mounted image sensor 21. Further, the plurality of first terminals 10 are provided corresponding to the plurality of first openings 7. The first terminal 10 has a substantially circular shape in a plan view. The first terminal 10 is filled in the first opening 7 and is exposed from the base insulating layer 4 when viewed from one side in the thickness direction. One surface 10A of the first terminal 10 in the thickness direction has a flat (smooth) shape. One surface 10A of the first terminal 10 in the thickness direction is substantially flush with one surface 4A of the base insulating layer 4. As a result, the first terminal 10 is arranged on one surface 4A of the base insulating layer 4.

As shown in FIG. 1, the plurality of second terminals 11 are aligned and arranged at the external component connecting portion 3 at intervals from each other. The plurality of second terminals 11 are provided so as to correspond to a plurality of terminals (not shown) of the external component. Further, the plurality of second terminals 11 are provided corresponding to the plurality of second openings 8. The second terminal 11 has a substantially rectangular shape (rectangular shape) in a plan view. The second terminal 11 is filled in the second opening 8 and is exposed from the base insulating layer 4 when viewed from one side in the thickness direction. One surface of the second terminal 11 in the thickness direction is substantially flush with one surface 4A of the base insulating layer 4. As a result, the second terminal 11 is arranged on one surface 4A of the base insulating layer 4.

As shown in FIG. 2, the plurality of wirings 9 are arranged on the other side in the thickness direction with respect to the base insulating layer 4, and specifically, are arranged on the other surface 4B of the base insulating layer 4.

The plurality of wirings 9 electrically connect the plurality of first terminals 10 and the plurality of second terminals 11. Specifically, one end of each wiring 9 falls from the other surface 4B into the first opening 7 and is continuous with each first terminal 10. The other end of each wiring 9 falls from the other surface 4B into the second opening 8 and is continuous with each second terminal 11.

Examples of the material of the conductor pattern 5 include metal materials such as copper, silver, gold, nickel or alloys containing them, and solder, and copper is preferable.

The thickness of the conductor pattern 5 is, for example, 1 μm or more, preferably 2 μm or more, for example, 15 μm or less, preferably 10 μm or less.

The cover insulating layer 6 is arranged on the other side in the thickness direction with respect to the base insulating layer 4 so as to cover the conductor pattern 5, and specifically, is arranged on the other surface 4B of the base insulating layer 4. The outer shape of the cover insulating layer 6 is formed to be the same as the outer shape of the base insulating layer 4.

Examples of the material of the cover insulating layer 6 include an insulating material. Examples of the insulating material include synthetic resins such as polyimide, polyamideimide, acrylic, polyethernitrile, polyether sulfone, polyethylene terephthalate, polyethylene naphthalate, and polyvinyl chloride. As the insulating material, preferably, the same polyimide as the base insulating layer 4 can be mentioned.

The thickness of the cover insulating layer 6 is, for example, 1 μm or more, preferably 2 μm or more, for example, 30 μm or less, preferably 10 μm or less, and more preferably 5 μm or less.

The thickness of such a mounting substrate 1 (the total thickness of the base insulating layer 4, the conductor pattern 5, and the cover insulating layer 6) is, for example, 3 μm or more, for example, 50 μm or less, preferably 30 μm or less.

2. 2. Manufacturing Method of Image Sensor Mounting Board Next, a manufacturing method of the mounting board 1 will be described with reference to FIGS. 3A to 3D. The method for manufacturing the mounting substrate 1 includes, for example, a metal support preparation step, a base insulating layer forming step, a conductor pattern forming step, and a cover insulating layer forming step in order.

As shown in FIG. 3A, in the metal support preparation step, the metal support 19 as an example of the metal support layer is prepared.

The metal support 19 has a flat plate shape having a substantially rectangular shape in a plan view. The upper surface of the metal support 19 has a flat (smooth) shape.

Examples of the material of the metal support 19 include metal materials such as stainless steel, 42 alloy, and aluminum, and stainless steel is preferable.

The thickness of the metal support 19 is, for example, 5 μm or more, preferably 10 μm or more, and for example, 50 μm or less, preferably 30 μm or less.

Subsequently, in the base insulating layer forming step, the base insulating layer 4 containing the above-mentioned polyimide, the above-mentioned development accelerator, and the above-mentioned photosensitizer is formed on the upper surface of the metal support 19. The thickness direction of the base insulating layer 4 shown in FIGS. 3A to 3D is opposite to the thickness direction of the base insulating layer 4 shown in FIG. 2, with the upper side of the paper surface being the other side in the thickness direction and the lower side of the paper surface being one side in the thickness direction. On the side. That is, one surface 4A of the base insulating layer 4 comes into contact with the metal support 19, and the other surface 4B of the base insulating layer 4 is located on the opposite side of the metal support 19 with respect to the one surface 4A.

Specifically, the base insulating layer forming step includes a step of applying a varnish as a material of the base insulating layer 4 on the metal support 19, a step of exposing and developing the applied varnish, and a step of heating the developed varnish. Including the process of

The varnish contains a polyamic acid as an example of a polyimide precursor, the above-mentioned development accelerator, and the above-mentioned photosensitizer.

The polyamic acid is a reaction product of the above-mentioned acid dianhydride component and the above-mentioned diamine component. For example, the above-mentioned acid dianhydride component and the above-mentioned diamine component are reacted in the presence of an organic solvent, for example, under the conditions of 15 ° C. or higher and 40 ° C. or lower, 0.2 hours or longer and 72 hours or lower. This prepares the polyamic acid.

The organic solvent can dissolve the above-mentioned acid dianhydride component and the above-mentioned diamine component. Examples of the organic solvent include polar aprotons such as N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, acetonitrile and the like. The organic solvent can be used alone or in combination of two or more.

Among the organic solvents, polar aprotons are preferable, and N-methylpyrrolidone is more preferable. The content ratio of the organic solvent can be changed as appropriate.

The content ratio of the development accelerator in the varnish is, for example, 30 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of polyamic acid.

The content ratio of the photosensitizer in the varnish is, for example, 10 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of polyamic acid.

Then, the varnish is applied to the entire upper surface of the metal support 19 and dried. As a result, the organic solvent volatilizes and a base film is formed.

The base film is then exposed through a photomask having a pattern corresponding to the openings (first opening 7 and second opening 8). Then, the base film is developed.

Next, the developed base film is heated and cured.

The heating temperature is 300 ° C. or higher, preferably 330 ° C. or higher, 400 ° C. or lower, preferably 380 ° C. or lower.

The heating time is 100 minutes or more, preferably 110 minutes or more, more preferably 120 minutes or more, for example, 500 minutes or less, preferably 400 minutes or less, still more preferably 350 minutes or less.

When the heating temperature is equal to or higher than the above lower limit and the heating time is equal to or higher than the above lower limit, the polyamic acid is imidized to form a polyimide, and most of the above-mentioned development accelerator and photosensitizer are removed. Therefore, the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4 can be adjusted to the above upper limit or less. Further, when the heating temperature is not more than the above upper limit, the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4 can be secured to be more than the above lower limit.

As a result, the base insulating layer 4 containing the polyimide is formed on the metal support 19.

Subsequently, as shown in FIG. 3B, in the conductor pattern forming step, the conductor pattern 5 is formed in the above-mentioned pattern with the upper surface (the other surface 4B) of the base insulating layer 4 and the first opening 7 and the second opening 8. It is formed on the upper surface of the metal support 19 exposed from, for example, by an additive method or the like.

As a result, the plurality of first terminals 10, the plurality of second terminals 11, and the plurality of wirings 9 are collectively formed. The first terminal 10 is arranged in the first opening 7 and comes into contact with the upper surface of the metal support 19. Although not shown, the second terminal 11 is arranged in the second opening 8 and comes into contact with the upper surface of the metal support 19. As a result, the first terminal 10 and the second terminal 11 are arranged on one surface 4A of the base insulating layer 4. Further, the wiring 9 is arranged on the other surface 4B of the base insulating layer 4.

Subsequently, as shown in FIG. 3C, in the cover insulating layer forming step, the cover insulating layer 6 is formed on the upper surface (the other surface 4B) of the base insulating layer 4 so as to cover the conductor pattern 5. The cover insulating layer forming step can be carried out in the same manner as the base insulating layer forming step.

Subsequently, as shown in FIG. 3D, the metal support 19 is removed in the metal support removing step.

As a method for removing the metal support 19, for example, a method of peeling the metal support 19 from the lower surface (one surface 4A) of the base insulating layer 4, for example, etching the metal support 19 (for example, dry etching, wet etching, etc.). How to do it.

Among the methods for removing the metal support 19, etching is preferable, and wet etching is more preferable.

When the metal support 19 is wet-etched, for example, a ferric chloride solution is used as the etching solution. Then, for example, the metal support 19 is removed by spraying the etching solution from one side in the thickness direction with respect to the metal support 19.

Then, one surface 4A of the base insulating layer 4, one surface 10A of the first terminal 10, and one surface (not shown) of the second terminal 11 are exposed.

As described above, the mounting substrate 1 including the base insulating layer 4, the conductor pattern 5, and the cover insulating layer 6 is manufactured.

3. 3. Method of Mounting an Image Sensor on a Mounting Board Such a mounting board 1 is provided with, for example, an image pickup device such as a camera module on which an image pickup device is mounted.

Next, a method of mounting the image pickup device 21 on the mounting board 1 will be described with reference to FIGS. 4E and 4F.

The method of mounting the image pickup device 21 on the mounting board 1 includes an element connection step and an underfill forming step.

As shown in FIG. 4E, in the element connection step, first, the image sensor 21 is prepared.

The image pickup device 21 is a semiconductor device that converts light into an electric signal, and examples thereof include solid-state image pickup devices such as a CMOS sensor and a CCD sensor. The image pickup device 21 is formed in a flat plate shape having a substantially rectangular shape in a plan view, and includes silicon such as a Si substrate, a photodiode (photoelectric conversion element) arranged on the silicon substrate, and a color filter (not shown). The image sensor 21 includes a plurality of terminals 25. The plurality of terminals 25 correspond to the plurality of first terminals 10.

Then, a bonding material 26 such as a solder bump is arranged on the first terminal 10 of the mounting board 1, and the first terminal 10 of the mounting board 1 and the terminal 25 of the image sensor 21 are electrically connected via the bonding material 26. Connecting.

As a result, the image sensor 21 is arranged at the center of the housing arrangement portion 2 of the mounting substrate 1, and is flip-chip mounted on the mounting substrate 1. At this time, the image sensor 21 is located on one side in the thickness direction with a distance from the one surface 4A of the base insulating layer 4.

Next, as shown in FIG. 4F, in the underfill forming step, an underfill layer 18 as an example of the second insulating layer is formed between the image pickup device 21 and the base insulating layer 4.

Specifically, the liquid resin composition is injected between the image pickup device 21 and one surface 4A of the base insulating layer 4, and then heat-cured.

Examples of the material of the underfill layer 18 include resin materials such as epoxy resin, polyurethane resin, silicone resin, and polyester resin, and epoxy resin is preferable. The material of the underfill layer 18 can be used alone or in combination of two or more.

The heating temperature is appropriately changed depending on the material of the underfill layer 18, and is, for example, 100 ° C. or higher, preferably 120 ° C. or higher, for example, 150 ° C. or lower, preferably 130 ° C. or lower.

The heating time is appropriately changed depending on the material of the underfill layer 18, but is, for example, 10 minutes or more, preferably 30 minutes or more, for example, 120 minutes or less, preferably 60 minutes or less.

As a result, the underfill layer 18 is formed between the image pickup device 21 and the one surface 4A of the base insulating layer 4. In other words, the underfill layer 18 is arranged on one surface 4A of the base insulating layer 4. That is, the mounting substrate 1 on which the image pickup device 21 is mounted includes the underfill layer 18.

As described above, the mounting of the image sensor 21 on the mounting substrate 1 is completed. The mounting substrate 1, the image sensor 21, and the underfill layer 18 form an image pickup unit 27.

Further, the mounting substrate 1 is not an image pickup device described later, but a component of the image pickup device, that is, a component for manufacturing the image pickup device, and is an industrially applicable device. The mounting substrate 1 may be distributed as a single component that does not include an image sensor, or may be distributed as an image pickup unit on which an image sensor is mounted.

4. Imaging Device Next, an imaging device 20 including an imaging unit 27 will be described with reference to FIG.

The image pickup apparatus 20 includes an image pickup unit 27, a housing 22, an optical lens 23, and a filter 24.

The image pickup unit 27 includes a mounting substrate 1, an image pickup element 21, and an underfill layer 18.

The housing 22 is arranged in the housing arrangement portion 2 of the mounting substrate 1 so as to surround the housing 22 with a distance from the image sensor 21. The housing 22 has a tubular shape having a substantially rectangular shape in a plan view.

The optical lens 23 is arranged on the opposite side of the mounting substrate 1 with respect to the image pickup device 21 at intervals in the thickness direction. The optical lens 23 is formed in a substantially circular shape in a plan view, and is fixed to the housing 22 so that light from the outside reaches the image pickup device 21.

The filter 24 is arranged between the image sensor 21 and the optical lens 23 in the thickness direction at intervals from the image sensor 21, and is fixed to the housing 22.

As shown in FIG. 4F, the present inventors under the base insulating layer 4 when the imaging device 20 (imaging unit 27) is placed under moist heat conditions (for example, 100 ° C. or higher and relative humidity of 80% or higher). It was found that the adhesion of the fill layer 18 is reduced.

Therefore, the present inventors have examined various findings, and the decrease in the adhesion of the underfill layer 18 under moist heat conditions is the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4. The present invention was completed by finding that it depends on.

As shown in FIG. 4F, in the mounting substrate 1, the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4 is equal to or higher than the above lower limit. Therefore, even when the image pickup apparatus 20 (imaging unit 27) is placed under moist heat conditions, it is possible to suppress a decrease in the adhesion of the underfill layer 18 to the base insulating layer 4.

Further, the total of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4 is not more than the above upper limit. Therefore, when the image sensor 21 mounted on the mounting board 1 is removed from the mounting board 1 and reworked, the underfill layer 18 can be peeled off from the base insulating layer 4. As a result, the reworkability of the image sensor 21 can be ensured.

The development accelerator also contains an imide acrylate compound and / or a polyethylene glycol compound. Therefore, while the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4 can be adjusted within the above range, the photosensitivity of the varnish containing the polyimide precursor, the development accelerator, and the photosensitizer Can be secured.

Further, in the method for manufacturing the mounting substrate 1, as shown in FIGS. 3A to 3D, a varnish containing a polyimide precursor, a development accelerator, and a photosensitizer is applied onto the metal support 19, and then the varnish is used. The (base coating) is exposed and developed, and then the varnish (base coating) is heated to the above heating temperature and the above heating time to form the base insulating layer 4.

Therefore, the total of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer 4 can be adjusted within the above range. As a result, the above-mentioned mounting substrate 1 can be efficiently manufactured by a simple method.

<Modification example>
In the above-described embodiment, the image pickup device mounting board 1 (mounting board 1) for mounting the image pickup device 21 is described as the wiring circuit board of the present invention, but the application of the wiring circuit board is not limited to this. .. For example, it is suitably used for FPCs used in smartphones, personal computers, game machines, and the like.

Further, in the mounting substrate 1, layers adjacent to each other in the thickness direction are adhesive-less FPCs that are adhered without an adhesive, but the present invention is not limited to this. An adhesive layer may be provided between layers adjacent to each other in the thickness direction. On the other hand, from the viewpoint of thinning, it is preferable that the mounting substrate 1 is an adhesive-less FPC as in the above embodiment.

Further, as shown in FIG. 2, the mounting board 1 includes a base insulating layer 4, a conductor pattern 5, and a cover insulating layer 6, but the configuration of the mounting board 1 is not limited to this. For example, the mounting substrate 1 may be further provided with a shield layer that is arranged on one side of the cover insulating layer 6 in the thickness direction and blocks electromagnetic waves from the outside, and a second cover insulating layer that covers the shield layer.

Further, in the image pickup apparatus 20, as shown in FIG. 5, the image pickup device 21 is flip-chip mounted on the mounting substrate 1, but can also be mounted on the mounting substrate 1 by wire bonding.

Even in such a modified example, the same effect as that of the above-described embodiment is obtained. Moreover, the above-described embodiment and the modified example can be appropriately combined.

A reference example and a reference comparative example are shown below, and the present invention will be described in more detail. The present invention is not limited to Reference Examples and Reference Comparative Examples. In addition, specific numerical values such as the compounding ratio (content ratio), physical property values, and parameters used in the following description are the compounding ratios corresponding to those described in the above-mentioned "Form for carrying out the invention". Substitute for the upper limit (numerical value defined as "less than or equal to" or "less than") or lower limit (numerical value defined as "greater than or equal to" or "exceeded") such as content ratio), physical property value, and parameters. it can.

Manufacturing example 1
2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (TFMB, aromatic diamine having a haloalkyl group as a substituent) 4.0 g (20 mmol) and p-phenylenediamine (PPD, aromatic) 8.65 g (80 mmol) of diamine) was placed in a 500 ml separable flask, dissolved in 200 g of dehydrated N-methyl-2-pyrrolidone (NMP), and the liquid temperature was raised to 50 ° C. by an oil bath under a nitrogen stream. It was monitored with a thermocouple so as to be, and stirred while heating. After confirming that they were completely dissolved, 29.4 g of 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA, aromatic dianhydride) was added to the solution over 30 minutes. (100 mmol) was added to a separable flask, and the mixture was stirred at 50 ° C. for 5 hours and then cooled to room temperature to obtain a polyimide precursor solution.

Next, in the polyimide precursor solution, 74 parts by mass of n-acryloyloxyethyl hexahydrophthalimide (development accelerator) and 1-ethyl-3, with respect to 100 parts by mass of the solid content (polyamic acid) of the polyimide precursor solution. A varnish was prepared by adding 14 parts by mass of 5-dimethoxycarbonyl-4- (2-nitrophenyl) -1,4-dihydropyridine (photosensitizer).

Reference Examples 1 and 2 and Reference Comparative Example 1
A metal support made of stainless steel is prepared, the varnish prepared in Production Example 1 is applied to the upper surface of the metal support, and then dried at 80 ° C. for 10 minutes to form a base film (polyimide precursor film). Formed.

Subsequently, the base film was exposed and developed, and then cured under a nitrogen atmosphere at the heating temperature and heating time shown in Table 1. As a result, a base insulating layer containing polyimide was formed.

Next, the ferric chloride aqueous solution (etching solution) was sprayed on the metal support to remove the metal support. As a result, one side of the base insulating layer was exposed.

From the above, a base insulating layer was obtained.

In each base insulating layer, the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer was measured. The results are shown in Table 1.

In addition, it was confirmed by FT-IR that the curing of all the base insulating layers was completed.

Reference comparison example 2
Kapton 100H (manufactured by DuPont) was prepared as a base insulating layer. Kapton 100H did not contain a development accelerator and a photosensitizer.

<Initial adhesion of underfill layer>
An underfill layer was formed on one surface of the base insulating layer of each reference example and each reference comparative example, and the initial adhesion of the underfill layer to the base insulating layer was measured.

Specifically, a liquid epoxy resin composition was applied to one surface of the base insulating layer after the PCT test, and then dried at 125 ° C. for 10 minutes to form an underfill layer. The thickness of the underfill layer was about 40 μm.

Next, a double-sided tape (No. 5000ns, manufactured by Nitto Denko Co., Ltd.) was attached to the surface of the underfill layer opposite to the base insulating layer to prepare a laminate. The laminate includes a base insulating layer, an underfill layer, and double-sided tape in this order in the thickness direction.

Next, the laminate was cut into a flat strip having a width of 5 mm, and the laminate was fixed to a sample table provided with the following device with double-sided tape. The sample table had a cylindrical shape that was rotatably supported, and the outer diameter of the sample table was 20 cm. Further, the laminated body was adhered to the peripheral surface of the sample table.

Next, the base insulating layer was peeled off from the underfill layer under the following conditions. The results are shown in Table 1.

Equipment; SVZ-50NB (manufactured by IMADA)
Tensile angle: 90 ° (that is, the tensile direction is the radial direction of the sample table)
Tensile speed: 10 mm / min <Rate of decrease in adhesion of underfill layer after moist heat>
Prior to the measurement of the adhesive force, a pressure cooker test (PCT test) was performed on the base insulating layer of each reference example and each reference comparative example. Specifically, each base insulating layer was placed under the conditions of 120 ° C., 100% relative humidity, and a pressure of 1.9 atm for 100 hours.

Then, in the same manner as described above, an underfill layer was formed on one surface of the base insulating layer after the PCT test, and the adhesion of the underfill layer to the base insulating layer after the PCT test was measured. Then, the rate of decrease in the adhesion of the underfill layer after the PCT test (adhesion after the PCT test / initial adhesion) was calculated. The results are shown in Table 1.

<Discussion>
As shown in Table 1, in Reference Example 1 in which the sum of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer is 50 ppm or less, the content ratio of the development accelerator and the photosensitivity in the base insulating layer Compared with Reference Comparative Example 1 in which the sum with the content ratio of the agent exceeds 50 ppm, the adhesion of the underfill layer to the base insulating layer after the PCT test (that is, after being placed under moist heat conditions) is reduced. It is significantly suppressed.

Further, in Reference Example 1, the total of the content ratio of the development accelerator and the content ratio of the photosensitizer in the base insulating layer is 5 ppm or more, and the initial adhesion of the underfill layer to the base insulating layer is 200 gf / cm or less. It has been adjusted. If the adhesion exceeds 200 gf / cm as in Reference Comparative Example 2, it is difficult to peel off the underfill layer from the base insulating layer when the electronic component is reworked. In this respect, in Reference Example 1, the adhesion is 100 gf / cm or less, and the reworkability of the electronic component can be ensured.

1 Mounting board 4 Base insulation layer 4A One side 10 1st terminal 18 Underfill layer

Claims (3)

A first insulating layer containing polyimide, a development accelerator, and a photosensitizer,
A terminal arranged on one surface in the thickness direction of the first insulating layer is provided.
A wiring circuit board, wherein the total of the content ratio of the development accelerator and the content ratio of the photosensitizer in the first insulating layer is 5 ppm or more and 50 ppm or less. The wiring circuit board according to claim 1, wherein the development accelerator contains an imide acrylate compound and / or a polyethylene glycol compound. The process of preparing the metal support layer and
A step of forming a first insulating layer containing a polyimide, a development accelerator, and a photosensitizer on the metal support layer.
A step of forming a terminal on one surface of the first insulating layer in the thickness direction is included.
The step of forming the first insulating layer is
A step of applying a varnish containing a polyimide precursor, a development accelerator, and a photosensitizer onto the metal support layer.
The steps of exposing and developing the varnish,
A method for manufacturing a wiring circuit board, which comprises a step of heating the developed varnish to 300 ° C. or higher and 400 ° C. or lower for 100 minutes or longer.

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